A relational symbol denoting non-congruence between geometric figures, numbers, or algebraic expressions in mathematics.
Examples
Non-congruent triangles
\triangle ABC \ncong \triangle DEF
Non-congruent numbers in modular arithmetic
15 \ncong 3 \pmod{7}
Non-congruent geometric figures with different areas
\text{Area}(P_1) = 16, \text{Area}(P_2) = 25 \implies P_1 \ncong P_2